Lucy Mangan: Natural gas

It is, truth be told, rare that I am genuinely moved by the spirit of journalistic inquiry, but my recent experiences at the gentle hands of yoga have made me so. However, while this column is about to take on an investigative tone, I should warn you that it will be dealing with matters semi-scatological, so those of you with delicate sensibilities, go and read an improving book until I'm done.

Yoga, I have discovered through personal humiliation and the reports, in all senses, of others, makes you fart. By the end of an hour we sound like a meeting of Flatulents Anonymous.

Now, I have noticed over time that one of the few compensations for doing vigorous exercise comes - between 12 and 24 hours later - in the form of a decent poo. Sometimes, frankly, it is only the promise of this most primal of satisfactions that keeps me going. The process makes sense: you jump up and down, shuggle your insides around enough, and anything not firmly anchored by veins, arteries and visceral ropework will naturally obey the forces of gravity. But it doesn't, as yoga does, turn me into an ambulant wind turbine.

So why does a bit of stretching have such a violent effect on the gaseous and potentially cacophonous content floating about within the intestinal tract? Resisting the temptation to type the words "fart expert" into Google, I instead avail myself of the massive resources of the Guardian. A series of furtive phone calls and microfiches left at dead-letter drops that only the most flexibly jointed can reach leads me eventually to a nameless spokeswoman from the British Yoga Teachers Organisation. "When you are working on the manipura chakra, which is aligned with the navel, where the intestinal area is," she says, "people do tend to break wind, and burp too. Holding certain postures and working slowly massages the organs and has a releasing effect. It is about changing the flow of energy - prana - and detoxifying the body. Part of that is expelling unwanted gases."

So there you have it, good people. We must learn to fart, and be free.